In the last few days we've been experiencing OSPF drops between our main site and two branch offices. I'm seeing no drops on the interfaces, no errors, link remains up/up. The problem appears only for a few minutes, then goes away. We have see this happen 4 times in the last few days, no correlation in times.

Both VLANs ride a 10Gig link to our ISP, where they split into 1Gig links to our far end routers:

interface TenGigabitEthernet1/4

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1679,1812

switchport mode trunk

logging event link-status

mls qos trust dscp

no cdp enable

At the other end:

interface Vlan1679

bandwidth 1000000

ip address 172.30.174.26 255.255.255.252

no ip redirects

no ip unreachables

ip pim sparse-mode

ip ospf cost 5

logging event link-status

ipv6 address FD0B:7CDB:AEFD:7C24::2/64

ipv6 ospf cost 5

ipv6 ospf 6000 area 25

interface Vlan1812

bandwidth 1000000

ip address 172.30.176.54 255.255.255.252

no ip redirects

no ip unreachables

ip pim sparse-mode

ip ospf cost 105

logging event link-status

ipv6 address FD0B:7CDB:AEFD:7C27::2/64

ipv6 ospf cost 110

ipv6 ospf 6000 area 25

I just recently added the bandwidth statements from a suggestion I got from another source. Would these bandwidth statements have any effect? I don't see how. Also, any other ideas on why we seem to not be receiving the OSPF keepalives correctly?

the bandwidth command will have no effect on OSPF adjacency flapping.All it will do is modify the metric of routes as far as OSPF is concerned( here it won't do anything for IPv4 as you entered the cost at the interface) and so may influence downstream path selection.It will also have effect on any QoS you have configured on the interface.

hello pls somebody help me....i have configured the ospf dead timers and hello timers.i wanna ask since on broadcast hello timer is 10 sec and dead timer is 40 sec.so the first router sends hello packets to second one every 10 sec and when the second router get hello its again update its dead timer to 40 sec.but when i chage the dead timers say dead timers is 36 sec and hello is 10 sec so i want to ask since my hello is 10 sec so why my first router not send hello to another router because it has 36 sec dead timers and hello is sending every 10 sec so when dead timers comes to 26 sec 1 hello will b receive and the dead timers should be updated to 36 sec.but nothing is happening like this.i just waana know why we need dead timers =4x always.